Issawi's health has severely deteriorated after an on-again, off-again hunger strike stretching more than 200 days. The 35-year-old Palestinian is set to be sentenced this month for violating the terms of an earlier release from prison and suffered a new setback on Tuesday when a Jerusalem judge rejected his request to be freed on bail.

The U.N. chief said Palestinian detainees should be charged and face trial or be promptly released, Nesirky said.

"The secretary-general urges for a solution to be reached without delay in order to resolve the prisoners' plight and preserve calm," he said.

Israel is holding some 4,500 Palestinians for charges ranging from throwing stones to undertaking deadly terrorist attacks. Their incarceration is an emotional issue for Palestinians, who see them as heroes of their struggle for liberation from Israeli occupation.

He also calls on Israel to ensure family visitation rights for prisoners and to respect the human rights of detainees, the spokesman said.

In Ban's conversation with Netanyahu, Nesirky said late Tuesday that the two leaders discussed the need for the resumption of Israeli-Palestinian peace negotiations and the situation in the Middle East, especially the impact of the Syrian conflict and concerns it has raised for Israel's security.

"The secretary-general stressed that it is urgent for Israelis and Palestinians to re-engage in a serious peace effort with effective international support, and to create a conducive environment to that end," Nesirky said.